The symbol for “null,” used when linguistic analysis requires you to say that you are “adding nothing” to a base form.
For instance, in languages with reasonably rich verb inflection, it is usual to say that you “add a personal ending” to the stem or base form of the verb, and you try to formulate a rule that accounts for a large number of verbs. Take the 2nd-conjugation Latin verb respondeo respondere.
- The base respond- plus the “thematic vowel” –e– gives you the stem: responde-
- To the stem responde- you add the personal endings –o -s -t -mus -tis -nt
- The result is the six personal forms of the present tense: respondeo, respondes, respondet, respondemus, respondetis, respondent.
Well, it sometimes happens, unfortunately, that, with some verbs or groups of verbs, time may have worn away completely a personal ending. In that case, do you say: “For this form (this particular person-number), we don’t add anything, even though in all other cases we do add a personal ending.” Certainly not! What kind of self-respecting rule would allow occasionally not obeying the rule? Instead, you say: “In this particular case, what we add as a personal ending is: null (= nothing = ∅). Here’s an example:
Formation of the Passé simple of –er Verbs
To the stem (e.g., aima-) add the personal endings:
- 1st-person singular: i > aimai
- 2nd-person singular s > aimas
- 3rd-person singular ∅ > aima
- and so forth…
Formation of the Present of Regular –re Verbs
To stem of an –er verb (e.g. répondre – re = répond-) add the personal endings
- 1st-person singular: s > réponds
- 2nd-person singular s > réponds
- 3rd-person singular ∅ > répond
- and so forth…